不同种植密度对留茬膜侧秋马铃薯病虫害的影响

调查了不同种植株行距下,留茬膜侧秋马铃薯的病株率和虫株率,结果表明,本次调查发现马铃薯虫害、病害共8种,分别为马铃薯二十八星瓢虫(Henosepilachna vigintioctomaculata Motschulsky)、茶黄螨(Polyphagotarsone-mus latus Banks)、茄无网蚜[Acyrthosiphon solani(Kaltenbach)],马铃薯生理性卷叶病、马铃薯病毒病(PVY)、马铃薯晚疫病(Phytophthora infestans Mont)、马铃薯软腐病(Erwinia carotovora subsp.)和马铃薯早疫病(Alternaria solani So-rauer),且病虫害的总发生率随着马铃薯种植密度的增加而增大,当行距30 cm、株距20 cm时,马铃薯产量最高。     

Branch thickness in unthinned stands of Sitka spruce (Picea sitchensis (Bong.) Carr.)

Results of branch measurings in unthinned stands of Sitka spruce in Denmark are presented. Three different measures of branch thickness are discussed in relation to visual grading of structural timber. On basis of the average thickest branch 5.0 m above ground it is recommended not to let spacing exceed 1.8x1.8 m‐2.0x2.0 m at establishment. Since Sitka spruce branches react profusely when spacing widens, this is the upper limit, presupposing a no‐thinning regime. With reference to the literature, the same recommendation can be given on basis of machine stress gradings.     

Stand responses to initial spacing in Norway spruce plantations in Norway

Abstract

Using data from nine spacing experiments of Norway spruce (Picea abies (L.) Karst.) in Norway, covering wide ranges of site index and initial spacing, this study evaluated stand basal area and volume responses to initial spacing and examined whether these responses varied by stand ages or site quality. We developed nonlinear regression models that described the standing basal area or volume responses to initial spacing along with site index and stand ages. The results show that closer spacings produced higher standing basal area and volume than wider spacings. The response curves are highly nonlinear in younger stands and become nearly linear in mid-rotation stands, indicating stronger responses at younger ages and weaker responses as age increases. Furthermore, for young stands, spacing effects are stronger at closer than at wider spacings. The basal area and volume responses to initial spacing tend to be similar across site indices. However, the interaction of site index and stand age on spacing responses makes it difficult to isolate the effect of site index on spacing responses. Mortality is higher and begins earlier at closer spacings than wider. The mean diameter of the largest 100, 400, 600, and 800 trees ha^?1 increased with spacing in three out of the nine experiments. Dominant height did not vary by initial spacing for any of the experiments. The findings suggest that the extra volume production in stands of closer initial spacing is restricted to early stand development.     

Influence of precommercial thinning grade on branch diameter and crown ratio in Pinus sylvestris in southern Sweden

Precommercial thinning is regarded as one of the most important measures for influencing timber quality in stands of Scots pine (Pinus sylvestris L.). The present study considers the influence of both thinning intensity and tree height at the time of thinning on diameter of the thickest branch and crown ratio. A total of 115 plots (either naturally regenerated, planted or sown, and either thinned down to 528–8000 stems?ha^?1 or untreated) included in 20 sites in southern Sweden were analysed. The average tree height after thinning varied from 1.2 to 8.3?m. An increasing number of remaining stems resulted in a reduction in branch diameter, although the reduction appeared to be only minor if the number of stems after thinning was more than 3000 stems?ha^?1. It was found that late thinning reduced the diameter of the thickest branch. The crown ratio decreased with stand height, number of stems after thinning and average height at thinning. The results were consistent for all trees and for the 500 thickest trees per hectare.     

Natural regeneration on planted clear‐cuts in boreal Sweden

Natural regeneration was registered on 97 clear‐felled and scarified sites in northeastern Sweden ten growing seasons after planting. On each site, three fix plots were laid out at planting and the planted seedlings were mapped. Ten years later all healthy non‐planted seedlings were registered in an anulus of size 15.7 m². Non‐planted seedlings were also observed in four 4 m² squares on each fix‐plot to estimate the zero‐square frequency. Species were classified as Pinus sylvestris, L., Picea abies (L) Karst. and deciduous species (Betula pendulajpubescens Roth./Ehrh., Populus tremula L., Alnus incana (L) Moench.). On average, 7 133 non‐planted seedlings ha^‐1 were found, of which 29% were conifers. Among the conifers, 71% were P. abies. More than 2 500 conifer non‐planted seedlings ha^‐1 were found on 27% of the plots. The number of non‐planted seedlings was correlated to the presence of neighbouring seed‐producing stands within 100 m and decreased with rising altitude. Pinus sylvestris seedlings were more frequent on dry soils while the deciduous seedlings were more frequent on wet sites. In the 4 m² squares, the zero‐square frequency was 29% if both conifers were and deciduous seedlings were considered and 63% if only conifers were considered. Mean height of the tallest seedling per species and square was 62 cm for P. sylvestris, 42 cm for P. abies and 107 cm for the deciduous seedlings. Key words: Alnus incana, Betula, broad‐leaves, deciduous, Norway spruce, Picea abies, Pinus sylvestris, Populus tremula, reforestation, Scots pine.     

Irradiance in young stands of picea abies (L.) karst. and pinus sylvestris L. and the possibilities to prevent suckers of broad‐leaved trees

Incoming shortwave global radiation (Q _g) and photosynthetically active radiation (PAR; Q _pa as a fraction of full daylight, relative irradiance (%Q), were measured at the same time in young stands of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.). Measurements were made on three levels above ground: 20 cm above ground and 50 and 15 % of stand height. Stands of three heights (75, 150 and 300 cm) were studied during two months. The stands were created by arranging young trees cut from natural stands, in nine quadratic spacings: 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1.0, 1.4 and 2.0 m. The leaf area index (L) was estimated. Differences in %Q‐values for Q _pa and Q_g in the same species and at the same stand height and level of light measurements above ground were significant only in 150 and 300 cm stands. In 75 cm high stands of Scots pine, the %Q was <60% at spacings <0.2 m and in 75 cm high stands of Norway spruce, the %Q was <60% at spacings <0.3 m. Only at 0.1x0.1–0.3x0.3 m, %Q was <20% in Norway spruce stands. In 150 cm stands %Q<20% was measured at spacings <0.7 m in Norway spruce and <0.5 in Scots pine. In 300 cm stands of Norway spruce it was measured up to 1.2 and in Scots pine <1.1 m. Light extinction coefficients, K and K_g for spruce and pine stands were 0.17–0.40 and 0.16–0.31 respectively. Some practical implications of the study are presented. Lack of light (%Q<10%) as a single factor of seriously suppressed growth and development of broad‐leaved plants and suckers by competition in young stands of spruce and pine only occur in dense stands 0.3x0.3 m‐1.1xl.l m (8000–100000 stems/hectare). Competition by light on a regenerated area generally occurs in the level of 50% of tree height (150–300 cm) and higher due to the rapid growth of broad‐leaved trees (sprouts) compared with planted conifers but the light intensity at these levels %Q>10%.     

栽种对象草生产性能的作用

对象草 Pennisetum purpureum 采用扦插、平埋2种植入方式和40、80、120 cm 3个行距水平进行组合栽种试验,结果表明,扦插和平埋的繁殖成活率分别为90%和87%,两者间的差异不显著(P<0.05).方差分析显示,行距水平间的草产量存在显著差异(F>F0.01),植入方式、植入方式与行距互作效应均不显著(F0.05).5次刈割的年合计产量表明,平埋 80 cm行距、平埋 40 cm行距的产量显著高于平埋 120 cm行距、扦插 120 cm行距的产量(P<0.05);平埋 80 cm行距与扦插 120 cm行距间的产量差异达到极显著水平(P<0.01).     

变行距水稻钵苗移栽机移栽装置设计与试验

针对现有水稻钵苗移栽机移栽行距固定、不能适应南方双季稻区不同行距移栽农艺要求的问题,在歩距式水稻插秧机基础上,设计了一种取苗轨迹简单、实用及性能可靠的变行距钵苗移栽装置。根据钵苗最佳拔取角度与取、投苗位置要求,确定取苗运动轨迹,设计取苗连杆机构,建立运动学模型,并应用Matlab对机构模型进行优化设计;根据取苗连杆机构运动参数与钵苗下落姿态的要求,设计苗夹开合与旋转运动控制凸轮,并进行取苗连杆机构与苗夹机构之间运动同步性的运动仿真分析;为满足钵苗经过输苗筒后下落至水田时刻的一致,以保证移栽时钵苗株距均匀性,对输苗筒的关键结构进行了理论分析及设计;进行不同取苗速度、不同行距的移栽试验,平均取苗成功率达到89.96%,平均倒苗率3.45%,表明该装置具有较好的移栽效果,可应用于水稻钵苗变行距移栽作业。     

宽垄大行栽培对温室番茄生理生态及产量的影响

【目的】研究不同栽培垄距对温室番茄生理生态、产量和品质的影响,为筛选温室番茄产量、品质最佳的垄距提供参考。【方法】以"普罗旺斯"番茄为材料,设置4个垄距处理,分别为1.1 (对照CK),1.3,1.5和2.0 m,对应垄宽+沟宽分别为80 cm+30 cm,80 cm+50 cm,80 cm+70 cm,80 cm+120 cm。测定并比较不同栽培垄距处理番茄生长发育、光合生理、产量、品质及温室主要生态因子指标,筛选温室番茄的最佳栽培垄距。【结果】随栽培垄距的增大,番茄地上部生长指标、根系生长指标、光合效率、产量和品质均呈先升高后降低趋势,番茄冠层气温、温室地温和CO_2浓度呈上升趋势,而相对湿度呈下降趋势。垄距1.5 m(即垄宽+沟宽为80 cm+70 cm)处理番茄生长势和产量、品质均最佳,产量为90 119.92 kg/hm~2,较对照(CK)提高16.87%;糖酸比为7.25,可溶性固形物含量为46.47 g/kg,维生素C、番茄红素含量分别为365.97和3.39 mg/kg,较对照(CK)分别提高54.91%,25.18%,28.12%和7.10%。【结论】适当加宽栽培垄距可提高番茄产量,改善果实品质,1.5 m(垄宽+沟宽80 cm+70 cm)为温室番茄最适宜的栽培垄距。     

薄壁微喷带组合均匀度及铺设间距试验研究

【目的】研究薄壁微喷带组合均匀度及最佳铺设间距。【方法】选取市场常用的N44 mm微喷带,开展不同压力下微喷带喷洒强度、均匀度和喷洒宽度试验,利用Surfer软件克里金插值法按照水量组合原理对数据进行网格化处理,在1.0~2.0 R(喷洒宽度)范围内,分析微喷带组合喷洒强度、组合均匀度,确定微喷带合理组合间距。【结果】发现单管微喷带喷洒强度随喷洒距离增大呈双峰或单峰分布,喷洒宽度也随压力的增大而增大。组合喷洒强度随铺设间距的增大而减小;组合均匀度随铺设间距增大呈"大-小-大-小"的趋势,当微喷带铺设间距为1.6 R时,组合均匀度达到峰值。【结论】针对市场上常用的折径44 mm微喷带,发现当铺设间距为1.8 R与1.9 R时,组合喷洒强度较小,组合均匀度较大,满足规范要求。